1. Field of the Invention
The present invention relates generally to a battery state diagnostic apparatus and more specifically to battery state diagnostic apparatus for a battery set having a plurality of battery modules, and a module charger/discharger.
2. Description of Related Art
In an electric car, it is usual to use battery sets which are each provided With a plurality of battery modules, However, whenever a problem occurs in a battery set, it is necessary to remove the battery set from the car and test each battery module one-by one in order to diagnose the abnormality, deterioration or the like which has occurred. When an abnormal module is found it must be replaced, and if life span of the battery set, the whole battery set must be replaced.
However, since it is necessary to identify the abnormal battery modules by individually testing each of the plurality of batteries constituting the battery set, in the case of a battery set used in an electric car which requires a high voltage source, there is a problem that the number of batteries to be diagnosed is very high, and the diagnosis process is time consuming and troublesome.
Further, SOC (state of charge) of the battery modules constituting the battery set varies with the usage environment, and when the abnormal battery module is replaced the SOC of the new replacement battery module does not always coincide with those of the other modules. If a replaced battery module having a notably different SOC is used with other battery modules, problems such that the replaced battery module may be induced to assume an excessively charged state or an excessively discharged state, tend to occur. This tends to result in the a battery set exhibiting poor performance.